Concentrated brines are frequently found within oil and gas wells and have applications in many industries including use in refrigeration, ship ballasting and mining operations. In the oil industry, heavy sodium chloride brines are often encountered within production zones.
Some types of brines may be introduced into a wellbore as part of the completion process. Common completion brines include NaBr, CaCl2, CaBr2, ZnBr2, HCOONa, HCOOK, HCOOCS. The density of synthetic brines may be as low as water or as high as 2.4 g/mL. Synthetic brines are mainly applied after the drilling and before the acidizing or fracturing of the well, which includes, displacement, running completion tools, packers, production tubing, etc. The purpose of the brine completion fluid is mainly to provide hydrostatic pressure to control the wells during displacement, completion or production operations. Concentrated synthetic brines, unlike drilling fluids, are free of suspended solids. Thus, in those cases where they enter oil or gas bearing formations, no damage (i.e. plugging) of the production zone occurs.
The densities of several saturated salt solutions are listed below in Table I:
TABLE ICompoundDensityConcentrationNaCl1.226%NaBr1.4140%HCOONa1.3244.7%  KCl1.1624%KBr1.3740%CsCl1.8864%CaCl21.440%CaBr21.8357%ZnBr22.3052.5%  When a wellbore is filled with such high-density fluids, the hydrostatic pressure is balanced by the formation pressure. Once the work is completed, it is necessary for the fluid to return to the surface of the well. A common well dewatering method consists of the addition of a foaming agent to the fluid inside the well. Gas is then used to convert the liquid into low-density foam. The foam, which produces only a fraction of the hydrostatic pressure of the liquid, flows out of the well with less pressure required than that for the non-foamed brine. In a similar fashion, if a well is producing brine, it can be removed from the well with foaming agent assistance, thereby preventing the phenomena of “drowning” the well. (“Drowning” refers to the filling of the well with water such that the well becomes “drowned”, thereby prohibiting the production of gas.)
Unfortunately, most foaming surfactants do not exhibit foaming abilities in concentrated brines. In many instances, surfactants will be salted out of solutions and precipitate. Even commercial products advertised as “brine foamers” fail in saturated and nearly saturated salt solutions. A foamer for use with concentrated brines is therefore needed.